This invention relates to a suspended ceiling construction for a clean room and retaining clips for holding removable fill-in panels, diffusers and light fixtures in place. Such elements are referred to below collectively as “removable ceiling components”.
In a clean room such as an operating room, the ventilation system must provide breathing air and comfort for the surgical team, and ventilating components must be arranged in the ceiling in such a manner that ceiling mounted operating room equipment and other ceiling penetrations are accommodated without themselves creating a pathway through which particles and microorganisms might enter the operating room. The system must also isolate the patient from as many airborne particles as possible, by employing suppression, dilution and filtration methods.
Research over the last two decades has increasingly shown that a properly designed and installed laminar (or “unidirectional”) ventilation system in an operating room or clean room can substantially reduce the number of airborne particles impacting a surgical site in an operating room, and that a correlation exists between the number of airborne particles and the rate of surgical site infections. United States National Institutes of Health (NIH) research has identified design criteria which, when employed in the design of operating room ventilation systems, can control and minimize the number of particles at the incision site. These parameters include air change rate, diffuser selection, filtration diffuser application, and return/exhaust location.
The rate at which air is replaced in a room is important in many clean room situations. Providing a minimum air change rate not only dilutes contaminants in the air, but also keeps the air fresh and minimizes the accumulation of odors. The number of air changes varies, as governed by the local authority having jurisdiction. NIH research has most recently shown that for a general purpose operating room, 20 air changes per hour are optimal. Higher air change rates are sometimes indicated for operating rooms where higher-risk procedures take place. These “ultraclean” operating rooms include orthopedic, bone marrow and large organ transplant rooms and some cardio rooms.
Typically, air enters operating rooms through diffusers. Unidirectional non-aspirating diffusers sometimes also called laminar flow diffusers or laminar flow modules are recommended by ASHRAE as a result of NIH and other research. The type and number of diffusers should be selected so that the resulting average velocity is in the range of 25-35 cubic feet per minute for every square foot of diffuser face. Within this operating range, unidirectional diffusers minimize the number of airborne particles drifting upward from the patient and the surgical team, while also minimizing the number of existing airborne particles blown downward toward the patient's incision.
The cleanest possible system results from a terminal HEPA filter mounted inside the unidirectional flow diffuser. This arrangement prevents any unseen ductwork contamination from entering the room.
If a clean room has a suspended ceiling, consideration must be given to preventing the infiltration of contaminates from the interstitial space above the suspended ceiling. Contamination can occur if a component such as a fill-in panel or a light fixture is unintentionally dislocated, such as during cleaning. To prevent such accidents, ceiling component retaining devices typically are installed from above the ceiling after the components are in place. However, this approach does not allow for subsequent convenient access to the interstitial space because there must be secondary access doors in the ceiling so that one can install or replace the retaining devices. Moreover, because the retaining devices are often damaged or destroyed when a ceiling component is removed, a supply of spare devices must be kept on hand.
Another problem is that when a ceiling component is replaced, the installer faces the problem of how to replace the hold down devices from above the ceiling after the component is in place. He may omit the devices if a secondary access door is not provided close enough to the component.
In general, ceiling component retaining devices should be invisible from the room side of the system to maintain the aesthetics of the system, and to avoid portions exposed on the room side, which might collect dust and result in unsanitary conditions.
It would be beneficial to have a simple retaining device for clean room ceiling panels and fixtures which would normally hold the panel securely in position in the ceiling grid, but would permit it to be removed from below when needed.